Nobuhiro Gemma

CARRIER INJECTION CHARACTERISTICS OF ORGANIC ELECTROLUMINESCENT DEVICES

The junction characteristics of metal/organic (M/Org) and organic/organic (Org/Org) interfaces, composing an organic electroluminescent (EL) device, M/Alq3/Diamine/ITO, were studied by measuring the displacement current characteristics of M/Org/Org/ SiO2/Si structures. The M/Alq3 junction was found to be both electron and hole injective, depending on the metal electrode. As for the Alq3/Diamine interface, it was found that two band offsets (Φ VB and Φ CB) existed for respective valence and conduction bands. Φ VB was not very large, and holes in Diamine were able to pass through into the adjacent Alq3 layer by applying a forward-bias, but Φ CB was so large that the electrons in Alq3 were blocked. Based on the standpoint that characteristics of the organic thin-film devices are governed by those junctions, we discussed carrier-injection mechanism, and explain the efficient EL emission.

Single-Nanoparticle Detection Using a Low-Aspect-Ratio Pore

We explored single-particle translocation through a low thickness-to-diameter aspect ratio Si(3)N(4) pore mimicking graphene nanopore structure by a resistive pulse method. Ionic conductance of 0.05 aspect ratio pores scales linearly with the diameter, indicating predominant contribution of the access resistance to the ion transport. We find that the access resistance changes little during particle translocation. Furthermore, we observe enhanced particle capture rates via the strong electric field extended outside the low-aspect-ratio pore mouth. We also demonstrate electrical discrimination of two different sized particles using the low-aspect-ratio pore sensor with the constant access resistance assumption. The present findings indicate the potential utility of nucleotide-sized graphene nanopores as an electrical sensing platform for single-base identification via transmembrane ionic current blockade detections.

In Vivo and In Vitro Studies Suggest a Possible Involvement of HPV Infection in the Early Stage of Breast Carcinogenesis via APOBEC3B Induction

High prevalence of infection with high-risk human papilloma virus (HPV) ranging from 25 to 100% (average 31%) was observed in breast cancer (BC) patients in Singapore using novel DNA chip technology. Early stage of BC demonstrated higher HPV positivity, and BC positive for estrogen receptor (ER) showed significantly higher HPV infection rate. This unique association of HPV with BC in vivo prompted us to investigate a possible involvement of HPV in early stages of breast carcinogenesis. Using normal breast epithelial cells stably transfected with HPV-18, we showed apparent upregulation of mRNA for the cytidine deaminase, APOBEC3B (A3B) which is reported to be a source of mutations in BC. HPV-induced A3B overexpression caused significant γH2AX focus formation, and DNA breaks which were cancelled by shRNA to HPV18 E6, E7 and A3B. These results strongly suggest an active involvement of HPV in the early stage of BC carcinogenesis via A3B induction.

Carrier injection characteristics of the metal/organic junctions of organic thin‐film devices

The junction characteristics of metal/organic thin film (M/Org) interfaces were investigated by measuring the displacement currents for the structure of M/Org/SiO2/Si devices. The observed currents were ascribed to the carriers injected from metal electrodes into organic films, which were markedly dependent both on metals and organic materials employed. The threshold bias for carrier injection was also found to be dependent on the metal work function. The results can thus provide some detailed information about the junction properties including the potential barriers formed at the M/Org interfaces.

The transport mechanism of stearic acid LB films on metal and semiconductor substrates

Abstract The electrical transport properties of stearic acid(SA) LB films on various substrates were investigated. The ohmic characteristics for a metal/SA/Cr structure directly showed the existence of short circuits in these LB films. The V-I characteristic for a metal/SA/Al structure was found to be tunneling conduction through an insulating oxide layer on the Al surface. The V-I characteristic for a metal/SA/semiconductor structure was similar to that for a metal/semiconductor Schottky junction. These results confirm the existence of short circuits in SA LB films on any kind of substrate. The consistency of the authors experimental results with those previously reported shows that the existence of short circuits is a general phenomenon, not limited to the authors experiments.

Measurements of Electrostatic Double-Layer Forces Due to Charged Functional Groups on Langmuir-Blodgett Films with an Atomic Force Microscope

Using an atomic force microscope, we measured the forces between a Si3N4 tip and monolayers with different polar functional groups ( –NH2, –COOH, –CONH2, and –OH) prepared by the Langmuir-Blodgett method while varying the pH value of aqueous solutions. The obtained force vs distance curves were related to the surface charges of the tip and the dissociation of the functional groups from the pH dependency, and the charged state of functional groups could thus be discerned. In addition, the electrostatic origin of the force has been confirmed assuming constant potentials on both surfaces.

Electrical Double-Layer Forces Measured with an Atomic Force Microscope while Electrochemically Controlling Surface Potential of the Cantilever

The atomic force microscope was used to detect electrostatic forces and estimate surface potentials of samples in aqueous solution by applying voltage to a conducting tip. We controlled surface potential of a Au-coated cantilever electrochemically, and measured force vs distance curves on monolayers with different kinds of functional groups. As a result, we detected force variation with applied voltage to the tip, and the direction of force variation was found to agree with the polarity of surface charges due to the dissociation of the functional groups.

Rapid genotyping of carcinogenic human papillomavirus by loop-mediated isothermal amplification using a new automated DNA test (Clinichip HPV™).

This study was designed to evaluate the Clinichip HPV test, a new DNA test that detects carcinogenic human papillomavirus (HPV) rapidly by loop-mediated isothermal amplification and performs genotyping of all 13 carcinogenic types using automated DNA chip technology with an assay time 2.5h. Using this test, 247 Japanese women (109 with normal cytology, 43 with cervical intraepithelial neoplasia grade 1, 60 with cervical intraepithelial neoplasia grade 2/3 and 35 with invasive cervical cancer) were tested for carcinogenic HPV genotypes. The results were compared to those obtained by the polymerase chain reaction-amplified DNA sequencing using 13 type-specific primers. Overall, there was very good agreement for the detection of carcinogenic HPV between the Clinichip test and direct sequencing, with 95.5% total agreement and a kappa value of 0.91. Comparison of the detection of individual HPV types shows that the overall agreement was also high (range: 96.8-100%). In women with cervical intraepithelial neoplasia grade 2 or worse, the detection rate of carcinogenic HPV was 95.7% by both the Clinichip test and the direct-sequencing method, indicating complete agreement between the two methods. In conclusion, it was found that the Clinichip test is a promising new laboratory method for genotyping of carcinogenic HPV.

Simple and accurate determination of CYP2D6 gene copy number by a loop-mediated isothermal amplification method and an electrochemical DNA chip

BACKGROUND A combination technology of a loop-mediated isothermal amplification (LAMP) method and an electrochemical DNA chip has been developed. In this study, the CYP2D6 gene copies were detected by this technology for determination of the functional CYP2D6*5 and CYP2D6*2x2 alleles. METHODS A set of LAMP primers was designed to coamplify the CYP2D6 gene, but not the CYP2D6*36, and the CYP2D8P gene, which would enable determination of the CYP2D6 gene copies by relatively comparing with the amount of the amplified products of CYP2D6 and CYP2D8P. The LAMP products were reacted with the electrochemical DNA chip using the DNA detection system Genelyzer that automatically controls hybridization reaction, washing, and electrochemical detection. To test the feasibility of the system, 16 samples that have various combinations of copy numbers were selected from pooled samples previously genotyped according to empirically well-authorized Southern blotting-based RFLP methods. RESULTS The CYP2D6 gene copies were consistent with the previous genotypes except a rare CYP2D6*18 allele probably due to mutation near the primer region. The results were completely reproducible in a blind test and were given within 1.5h. CONCLUSIONS This method offers a simple and accurate determination of the CYP2D6 gene copies and is expected to contribute to personalized medicine.

CMOS Integrated DNA Chip for Quantitative DNA Analysis

Quantitative gene expression analysis, based on an electrochemical DNA-detection method uses immobilized DNA probes on Au electrodes with diameters from 200mum to 2mum. Cyclic voltammetry is used to measure anodic current from the intercalators. The 25times3mm2 IC, fabricated in 1mum 2M CMOS, contains 40 electrodes, 1600 transistors and dissipates 150mW at plusmn3.3V